Modern C++ (i.e., C++11 and later) introduced "move only" types: types such
as std::unique_ptr<T> that can never be duplicated. They must never be
copied (by assignments and constructors), they must be "moved". The
implementation of lalr1.cc used to copy symbols (including their semantic
values). This commit ensures that values are only moved in modern C++, yet
remain compatible with C++98/C++03.
Suggested by Frank Heckenbach, who provided a full implementation on
top of C++17's std::variant.
See http://lists.gnu.org/archive/html/bug-bison/2018-03/msg00002.html,
and https://lists.gnu.org/archive/html/bison-patches/2018-04/msg00002.html.
Symbols (terminal/non terminal) are handled by several functions that used
to take const-refs, which resulted eventually in a copy pushed on the stack.
With modern C++ (C++11 and later) the callers must use std::move, and the
callees must take their arguments as rvalue refs (foo&&). In order to avoid
duplicating these functions to support both legacy C++ and modern C++, let's
introduce macros (YY_MOVE, YY_RVREF, etc.) that rely on copy-semantics for
C++98/03, and move-semantics for modern C++.
That's easy for inner types, when the parser's functions pass arguments to
each other. Functions facing the user (make_NUMBER, make_STRING, etc.)
should support both rvalue-refs (for instance to support move-only types:
make_INT (std::make_unique<int> (1))), and lvalue-refs (so that we can pass
a variable: make_INT (my_int)). To avoid the multiplication of the
signatures (there is also the location), let's take the argument by value.
See:
https://lists.gnu.org/archive/html/bison-patches/2018-09/msg00024.html.
* data/c++.m4 (b4_cxx_portability): New.
(basic_symbol): In C++11, replace copy-ctors with move-ctors.
In C++11, replace copies with moves.
* data/lalr1.cc (stack_symbol_type, yypush_): Likewise.
Use YY_MOVE to avoid useless copies.
* data/variant.hh (variant): Support move-semantics.
(make_SYMBOL): In C++11, in order to support both read-only lvalues,
and rvalues, take the argument as a copy.
* data/stack.hh (yypush_): Use rvalue-refs in C++11.
* tests/c++.at: Use move semantics.
* tests/headers.at: Adjust to the new macros (YY_MOVE, etc.).
* configure.ac (CXX98_CXXFLAGS, CXX11_CXXFLAGS, CXX14_CXXFLAGS)
(CXX17_CXXFLAGS, ENABLE_CXX11): New.
* tests/atlocal.in: Receive them.
* examples/variant.yy: Don't define things in std.
* examples/variant-11.test, examples/variant-11.yy: New.
Check the support of move-only types.
* examples/README, examples/local.mk: Adjust.
This generates less code, which is nicer to read, but also takes less
chances with compilers such as G++ 4.8 that are too strict and check
"dead code" (templated code that is not instantiated).
* data/c++.m4 (b4_symbol_type_declare, b4_symbol_type_define): When
variants are used, don't generate code meant for non variants.
See ea0db44fed. We also need to disable
the warning in the examples (but don't want to clutter the
documentation with such details).
* doc/bison.texi (scanner.ll): Disable Clang's -Wdocumentation.
While at it, hide the other kludges.
That's the version on Ubuntu Precise.
See also 1dac131ec4.
* src/flex-scanner.h: Disable -Wdocumentation.
* doc/bison.texi: Turn off a warning triggered by Flex 2.6.4.
We have failures on Flex output, which are probably related to an old
release. Let's check.
In file included from src/scan-code-c.c:3:
src/scan-code.c:2198:21: error: empty paragraph passed to '@param' command
[-Werror,-Wdocumentation]
* @param line_number
~~~~~~~~~~~~~~~~~^
* .travis.yml: here.
Running all these tests might be overkill: it is very long, and don't
need full portability checks. Besides, some tests under Valgrind are
too slow and get killed by the CI (timeout of 10min without output).
* .travis.yml: here.
We have some maintainer-check-foo and some maintainer-foo-check. Keep
only the former.
* tests/local.mk (maintainer-push-check, maintainer-xml-check)
(maintainer-release-check): Rename as...
(maintainer-check-push, maintainer-check-xml)
(maintainer-check-release): these.
Most of our variables for C++ flags are named FOO_CXXFLAGS, not
CXXFLAGS_FOO.
* configure.ac, tests/atlocal.in, tests/calc.at
(NO_EXCEPTIONS_CXXFLAGS): Rename as...
(CXXFLAGS_NO_EXCEPTIONS): this.
Clang++ issues warnings when it's used to compile C. This make target
is precisely checking whether we can do that.
* configure.ac (NO_DEPRECATED_CXXFLAGS): New.
* tests/atlocal.in: Use it.
This completes 2d7e743802.
Some shells don't grok "local var=`cmd`" very well: they need the rhs
to be quoted.
./examples/test: 72: local: you.,: bad variable name
FAIL examples/variant.test (exit status: 2)
Reported by Étienne Renault.
* examples/test (run): Quote the values in 'local' assignments.
With GCC7 we have warnings (false positive):
x8.c: In function 'x8_parse':
x8.c:1233:16: error: 'yylval' may be used uninitialized in this function [-Werror=maybe-uninitialized]
yylval = *yypushed_val;
~~~~~~~^~~~~~~~~~~~~~~
x8.c: In function 'x8_pull_parse':
x8.c:1233:16: error: 'yylval' may be used uninitialized in this function [-Werror=maybe-uninitialized]
yylval = *yypushed_val;
~~~~~~~^~~~~~~~~~~~~~~
See also 9645a2b20e.
* tests/local.at (AT_PUSH_IF): New.
(AT_BISON_OPTION_POPDEFS): Pop it, and pop AT_PURE_IF.
* tests/headers.at (Several parsers, Several parsers): Disable these
warnings when in push parser.
Currently, in glr.cc, we emit the definitions of basic_symbol and
symbol_type, although there are not used.
* data/c++.m4 (b4_public_types_declare): Extract these definitions from
here, and move them...
(b4_symbol_type_declare): here.
(b4_public_types_declare): Also remove the definition of the symbol
constructors.
* data/lalr1.cc (b4_shared_declarations): Adjust: call
b4_symbol_type_declare and b4_symbol_constructor_declare.
Some shells don't grok `local var=$val` very well: they need the rhs
to be quoted.
./examples/test: 66: local: you.,: bad variable name
FAIL examples/variant.test (exit status: 2)
Reported by Étienne Renault.
* examples/test (run): Quote the values in 'local' assignments.
The header generated for variants with assertions but without
locations, is not self-contained. Prepare a check for this.
* tests/headers.at (Sane headers): New, extracted from...
(Several parsers): here.
Benchmarks show that it is more efficient to keep this copy
constructor, rather than forcing the use of the default constructor
and then assignment.
This reverts commit 7ab25ad020.
* doc/bison.texi (A Complete C++ Example): Prefer throw exceptions
from the scanner.
Show the invalid characters.
Since the scanner sends exceptions, it no longer needs to report
errors, so we can get rid of the driver's routine to report error,
do it in yyerror.
Use @group/@end group to improve rendering.
This example uses the calcxx_ prefix for each class. That's uselessly
heavy.
* doc/bison.texi (A Complete C++ Example): Simplify the class names.
Since now 'driver' denotes the class, use 'drv' for the values.
Formatting changes.
On these tests, at -O2 and above, GCC 8 complains that yylval may be
uninitialized. But it seems wrong: it is initialized. Rather than
turning off the warning in the skeleton (hence possibility hiding
relevant warnings of user parsers), let's turn it off in the tests
only.
163: parse.error=verbose and consistent errors: FAILED (conflicts.at:625)
165: parse.error=verbose and consistent errors: lr.default-reduction=consistent FAILED (conflicts.at:635)
166: parse.error=verbose and consistent errors: lr.default-reduction=accepting FAILED (conflicts.at:641)
167: parse.error=verbose and consistent errors: lr.type=canonical-lr FAILED (conflicts.at:645)
168: parse.error=verbose and consistent errors: parse.lac=full FAILED (conflicts.at:650)
169: parse.error=verbose and consistent errors: parse.lac=full lr.default-reduction=accepting FAILED (conflicts.at:655)
We get:
input.c: In function 'yyparse':
input.c:980:9: error: 'yylval' may be used uninitialized in this function [-Werror=maybe-uninitialized]
YYSTYPE yylval YY_INITIAL_VALUE (= yyval_default);
^~~~~~
cc1: all warnings being treated as errors
See https://lists.gnu.org/archive/html/bison-patches/2018-08/msg00063.html.
* tests/conflicts.at (AT_CONSISTENT_ERRORS_CHECK): Disable
-Wmaybe-uninitialized.
Suggested by Rici Lake.
https://lists.gnu.org/archive/html/bug-bison/2018-08/msg00033.html
* doc/bison.texi: Complete description of the first node in the main
@menu.
(Push Decl): Remove the 'experimental' warnings about push parser.
Clarify that the push parser object can be reused in several parses.
Reported by Brooks Moses <[email protected]>
http://lists.gnu.org/archive/html/bison-patches/2018-02/msg00000.html
* data/lalr1.cc (YY_EXCEPTIONS): New.
Use it to disable try/catch clauses.
* doc/bison.texi (C++ Parser Interface): Document it.
* configure.ac (CXXFLAGS_NO_EXCEPTIONS): New.
* tests/atlocal.in: Receive it.
* tests/local.at (AT_FULL_COMPILE, AT_LANG_COMPILE):
Accept a new argument, extra compiler flags.
* tests/calc.at: Run the C++ calculator with exception support disabled.
Currently the examples are too dense, let's put empty lines where
'#line' would be issued. And also remove some spurious empty
lines (remains from @group, @end group, etc.).
* examples/extexi: Do that.
* examples/local.mk (extexiFLAGS): Rename as...
(EXTEXIFLAGS): this.
* examples/mfcalc/local.mk, examples/rpcalc/local.mk: Define the
programs in a more natural order, source, preproc, then linker.
* examples/test: Be ready to work on programs that are not in
a subdir.
* examples/variant.test: New.
* examples/local.mk: Use it.
* examples/variant.yy: Don't use 0 for nullptr.
Use a more natural output for a list of string.
Visual Studio issues a C4146 warning on '-static_cast<unsigned>(rhs)'.
The code is weird, probably to cope with INT_MIN. Let's go back to
using std::max (whose header is still included in position.hh...) like
originally, but with the needed casts.
Reported by 長田偉伸, and with help from Rici Lake.
See also
http://lists.gnu.org/archive/html/bug-bison/2013-02/msg00000.html
and commit 75ae829984.
* data/location.cc (position::add_): Take min as an int.
Use std::max.
While here, get rid of a couple of useless inlines.
* doc/bison.texi (Mid-Rule Actions): Restructure to insert...
(Typed Mid-Rule Actions): this new section.
Move the manual translation of mid-rule actions into regular actions
to...
(Mid-Rule Action Translation): here.
Reported by Jannick.
http://lists.gnu.org/archive/html/bug-bison/2017-05/msg00001.html
"Amusingly" enough, we have the same problem with %defines when the
parser file name has backslashes or quotes: we generate #includes with
an incorrect C string.
* src/output.c (prepare_symbol_definitions): Escape properly the file
names before passing them to M4.
* data/bison.m4, data/lalr1.cc: Don't simply put the file name between
two quotes (that should have been strong enough a smell...), expect
the string to be properly quoted.
* tests/synclines.at: New tests to check this.
Suggested by Paul Eggert.
* src/reader.c (find_start_symbol): Don't check 'res', we know it is
not null. That suffices to avoid the GCC warnings.
* bootstrap.conf: We don't need 'assume', which doesn't exist anyway.
In 0931d14728 I removed too many
initializations from some ctors: some were not about base ctors, but
about member variables. In fact, more of them were missing to please
GCC 8.
While at it, generate more natural code for C++ without variant:
instead of
template <typename Base>
parser::basic_symbol<Base>::basic_symbol (const basic_symbol& other)
: Base (other)
, value ()
{
value = other.value
}
generate
template <typename Base>
parser::basic_symbol<Base>::basic_symbol (const basic_symbol& other)
: Base (other)
, value (other.value)
{}
* data/c++.m4 (basic_symbol::basic_symbol): Always initialize 'value',
it might be a POD without a ctor.
* data/lalr1.cc (stack_symbol_type::stack_symbol_type): Likewise.
* data/variant.hh (variant::variant): Default initialize the buffer too.
GCC 8 issues warnings whose root cause was a bit hard to find.
calc.cc: In member function 'virtual int yy::parser::parse()':
calc.cc:810:18: warning: '*((void*)&<anonymous> +8)' may be used uninitialized in this function [-Wmaybe-uninitialized]
, location (l)
^
calc.cc: In member function 'void yy::parser::yypush_(const char*, yy::parser::stack_symbol_type&)':
calc.cc:810:18: warning: '*((void*)&<anonymous> +8)' may be used uninitialized in this function [-Wmaybe-uninitialized]
, location (l)
^
calc.cc: In member function 'void yy::parser::yypush_(const char*, yy::parser::state_type, yy::parser::symbol_type&)':
calc.cc:810:18: warning: '*((void*)&<anonymous> +8)' may be used uninitialized in this function [-Wmaybe-uninitialized]
, location (l)
^
The problem is with locations that don't have a constructor, such as
Span (in calc.cc) which is POD. It is POD on purpose: so that we can
use that structure to test glr.cc which cannot use non POD in its
(C) stacks.
* data/c++.m4 (basic_symbol): Also ensure that 'location' is
initialized.
With GCC 7.3.0 and Flex 2.6.4, we get warnings on all the generated
scanners:
examples/calc++/calc++-scanner.cc: In function 'void yyrestart(FILE*)':
examples/calc++/calc++-scanner.cc:1611:20: error: potential null pointer dereference [-Werror=null-dereference]
/* %endif */
~~~~~~~~~~~ ^
examples/calc++/calc++-scanner.cc:1607:19: error: potential null pointer dereference [-Werror=null-dereference]
/* %if-c-only */
~~~~~~~~~~~~~~~ ^
examples/calc++/calc++-scanner.cc:1611:20: error: potential null pointer dereference [-Werror=null-dereference]
/* %endif */
~~~~~~~~~~~ ^
examples/calc++/calc++-scanner.cc:1607:19: error: potential null pointer dereference [-Werror=null-dereference]
/* %if-c-only */
~~~~~~~~~~~~~~~ ^
cc1plus: all warnings being treated as errors
Obviously the lines are incorrect, and the warnings are emitted twice.
Still, let's get rid of these warnings.
* doc/bison.texi, src/flex-scanner.h: Disable these warnings in code
generated by Flex.
Commit 3df32101e7 introduced invalid C
code. Caught by GCC 7.3.0.
* bootstrap.conf (gnulib_modules): We need assume.
* src/reader.c (find_start_symbol): Fix the signature (too much C++,
sorry...).
Prefer 'assume' to 'assert', so that we don't have these warnings even
when NDEBUG is defined.
This file was meant to be shown as an example. Install it.
* README, data/README: Put Emacs metadata in the final section.
* examples/README: New.
* examples/variant.yy: Use %empty.
* examples/local.mk: Install both these files.
We currently generate copy constructors such as the following
one (taken from examples/variant.yy):
parser::stack_symbol_type::stack_symbol_type (const stack_symbol_type& that)
: super_type (that.state, that.location)
{
switch (that.type_get ())
{
case 3: // TEXT
case 8: // item
value.copy< ::std::string > (that.value);
break;
case 7: // list
value.copy< ::std::vector<std::string> > (that.value);
break;
case 4: // NUMBER
value.copy< int > (that.value);
break;
default:
break;
}
}
they are actually useless: we never need it.
* data/lalr1.cc: Don't generate the stack_symbol_type copy ctor.
Fix a typo so that instead of
basic_symbol::basic_symbol (typename Base::kind_type t, const int v)
we now generate
basic_symbol::basic_symbol (typename Base::kind_type t, const int& v)
* data/variant.hh (b4_basic_symbol_constructor_declare)
(b4_basic_symbol_constructor_define): Add missing reference.
Several features were flagged 'experimental' and waiting for user
feedback to 'stabilize', but i. AFAIK, no user ever reported anything
about them, ii. they'be been here long enough to prove they don't do
harm.
* doc/bison.texi: No longer experimental: default %printer and
%destructor (typed: <*> and untyped: <>), %define api.value.type union
and variant, Java parsers, XML output, LR family (lr, ielr, lalr),
semantic predicates (%?).
* tests/actions.at: Fix some log messages.
Prefer #error to fprintf: it fixes the invalid use of yyoutput in
%destructor, and it is an even stronger check: that the code is not
even emitted. The portability of #error is not really a problem here,
since the point is anyway to have the compilation fail.
Make sure that we cannot apply a type to the (main) action of a rule.
* src/reader.c (grammar_rule_check): Issue the warning.
* tests/input.at (Cannot type action): Check the warning.
Akim Demaille